1. Field of the Invention
This invention relates to refrigerant recovery and purification systems. More specifically it relates to an arrangement for testing the purity of the refrigerant which has been recovered and purified by such a system.
2. Description of The Prior Art
A wide variety of mechanical refrigeration systems are currently in use in a wide variety of applications. These applications include domestic refrigeration, commercial refrigeration, air conditioning, dehumidifying, food freezing, cooling and manufacturing processes, and numerous other applications. The vast majority of mechanical refrigeration systems operate according to similar, well known principals, employing a closed-loop fluid circuit through which a refrigerant flows. A number of saturated fluorocarbon compounds and azeotropes are commonly used as refrigerants in refrigeration systems. Representative of these refrigerants are R-12, R-22, R-500 and R-502.
Those familiar with mechanical refrigeration systems will recognize that such systems periodically require service. Such service may include removal, of, and replacement or repair of, a component of the system. Further during normal system operation the refrigerant can become contaminated by foreign matter within the refrigeration circuit, or by excess moisture in the system. The presence of excess moisture can cause ice formation in the expansion valves and capillary tubes, corrosion of metal, copper plating and chemical damage to insulation in hermetic compressors. Acid can be present due to motor burn out which causes overheating of the refrigerant. Such burn outs can be temporary or localized in nature as in the case of a friction producing chip which produces a local hot spot which overheats the refrigerant. The main acid of concern is HCL but other acids and contaminants can be produced as the decomposition products of oil, insulation, varnish, gaskets and adhesives. Such contamination may lead to component failure or it may be desirable to change the refrigerant to improve the operating efficiency of the system.
When servicing a refrigeration system it has been the practice for the refrigerant to be vented into the atmosphere, before the apparatus is serviced and repaired. The circuit is then evacuated by a vacuum pump, which vents additional refrigerant to the atmosphere, and recharged with new refrigerant. This procedure has now become unacceptable for environmental reasons, specifically, it is believed that the release of such fluorocarbons depletes the concentration of ozone in the atmosphere. This depletion of the ozone layer is believed to adversely impact the environment and human health. Further, the cost of refrigerant is now becoming an important factor with respect to service cost, and such a waste of refrigerant, which could be recovered, purified and reused, is no longer acceptable.
To avoid release of fluorocarbons into the atmosphere, devices have been provided that are designed to recover the refrigerant from refrigeration systems. The devices often include means for processing the refrigerants so recovered so that the refrigerant may be reused. Representative examples of such devices are shown in the following U.S. Pat. Nos.: 4,441,330 "Refrigerant Recovery And Recharging System" to Lower et al; 4,476,688 "Refrigerant Recovery And Purification System" to Goddard; 4,766,733 "Refrigerant Reclamation And Charging Unit" to Scuderi; 4,809,520 "Refrigerant Recovery And Purification System" to Manz et al; 4,862,699 "Method And Apparatus For Recovering, Purifying and Separating Refrigerant From Its Lubricant" to Lounis; 4,903,499 "Refrigerant Recovery System" to Merritt; and 4,942,741 "Refrigerant Recovery Device" to Hancock et al.
Following the operation of such systems to recover and purify refrigerant, it is desirable, before reusing the refrigerant, to test the purity of that refrigerant. At best, existing systems are provided with sight glasses which may give some indication of the present of moisture in the recovered refrigerant.
U.S. Pat. No. 4,923,806 entitled "Method and Apparatus for Refrigerant Testing In A Closed System" is assigned to the assignee of the present invention and is directed to a method and apparatus for detecting contaminants in a refrigerant medium. This patent teaches the use of single use transparent glass testing tubes which are sealed until used and which contain therein an oil removal section, a water removal and indicating section, and, an acid indicating section. In use, the ends of the glass testing tubes are broken off and the tube is placed in a tube holder apparatus which functions to seal the tube so that all of the refrigerant flows directed through the tube. The presence of contaminants is indicated by a color change which may be quantified by comparison to a color chart and/or the extent of the promulgation of the color change in the indicating media. The refrigerant sample is allowed to pass through the testing tube and then to the atmosphere. The venting of refrigerant gas to the atmosphere is not considered to be environmentally acceptable expedient.
A commonly assigned U.S. patent application, Ser. No. 612,641, filed on Nov. 13, 1990, discloses a system for sampling the purity of refrigerant flowing through a refrigeration circuit. This system makes use of the system of U.S. Pat. No. 4,923,806, described above. The system described in the above identified patent application is shown as applied to a refrigerant recovery and purification system. In that system the operator had two options with respect to the refrigerant purity sampling feature. The first option was not to select this mode of operation, in which case the sampling tube fixture may or may not contain a refrigerant quality testing tube. Accordingly, the fixture could be open to the atmosphere. The second option was to select the refrigerant purity sampling feature. In that case, the user was instructed to install a purity test tube into the fixture prior to the recovery/recycle operation, and, the unit was programmed to automatically perform the purity test at the end of the cycle selected.
It has been found that, particularly with more sensitive sampling tubes, moisture in the surrounding air, moisture in the tube holder, and/or moisture from previous refrigerant samples, has adversely affected the accuracy and repeatability of moisture level reading in this system.